The present invention relates to the field of communications electronics, and, more particularly, to a communications transceiver and related methods.
Digital communications over twisted copper wire pairs, or optical fiber pairs, are widely used for Local Area Networks (LANs), for example. The LAN typically connects multiple computer users to a server or other computer. A LAN transceiver, that is, a combination transmitter and receiver, is used to transmit data and receive data over the twisted pair or fiber pair.
One typical line of such high speed LAN transceivers is made by Pulse of San Diego, Calif. under the part number designations PE-68531G, PE-68532G, PE-68538G, and PE-68537G. Another similar line of transceiver are offered by Valor Electronics of San Diego, Calif. Different transceiver models are generally made to be compatible with existing communications standards, such as those of ANSI, IEEE, and ATM.
A typical LAN transceiver for communications over a twisted wire pair typically includes a jack housing having a recess for receiving a mating plug. The housing also typically contains a printed circuit board for mounting various components. A series of electrical conductors are carried within the recess and engage mating conductors on the plug. One common arrangement provides the circuit components within a jack housing that is compatible with an so-called xe2x80x9cRJ-45xe2x80x9d jack.
Transformers are typically mounted on the circuit board along with one or more active components, such as signal processing integrated circuits, for example. Filters and termination devices are connected to the transformers and positioned within the jack housing. Transmit and receive circuit components are connected to the respective filters and terminations. For the outbound or transmit direction, the transmitter electronics may include an encoder and a transmit amplifier. In the receive or inbound direction, the electronics may include an automatic gain control (AGC) amplifier, adaptive equalizer and decoder. In addition, a baseline restoration circuit may be connected to the decoder and a signal detect circuit coupled to the output of the adaptive equalizer. A series of such transceivers may be mounted on a mother circuit board to further process the signals.
Of course, shielding of various circuit components may be important for a high speed LAN transceiver. In particular, the transceivers made by Pulse may be supplied with an overall metallic case or shield to reduce electromagnetic interference (EMI) to other adjacent components and vice-versa. U.S. Pat. No. 5,518,423 to Green et al. also discloses a number of arrangements for an external housing shield.
Unfortunately, the functions being performed by the electronics within the relatively small housing the size of an RJ-45 jack has been increasing. Where only magnetics were once included within the housing, active electronics circuits are also provided. The active electronic components may be susceptible to EMI generated by the magnetic components for a twisted pair transceiver. Similarly, an optical transceiver may experience undesirable EMI coupling between the transmitter portion and the receiver circuit portion. Individual shields for the components may be ineffective or be difficult to assemble and thereby greatly add to the cost of manufacturing.
In view of the foregoing background, it is therefore an object of the present invention to provide a communications transceiver and associated method wherein the components or devices are less susceptible to EMI.
It is another object of the invention to provide a communications transceiver and associated method resistant to EMI and that is compact and is compatible with existing RJ-45 jacks and plugs.
These and other objects, features and advantages in accordance with the present invention are provided by a communications transceiver comprising a jack housing including portions defining a recess for receiving a mating plug therein, signal connector means within the recess for establishing inbound and outbound signal paths with corresponding signal connector means of the mating plug, and a circuit board within the jack housing and connected to the connector means. Moreover, the circuit board preferably comprises an electrically conductive layer defining a first internal electromagnetic interference (EMI) shield. Accordingly, at least one first circuit device being susceptible to EMI is mounted on a first side of the circuit board, and at least one second circuit device generating EMI is mounted on the circuit board on a second side thereof opposite the first side. The first internal EMI shield extends between the at least one first circuit device and the at least one second circuit device.
The transceiver may include an electrically conductive layer on outer surface portions of the jack housing defining an external EMI shield. The first internal EMI shield may be electrically connected to the external EMI shield.
The jack housing is preferably compatible with an RJ-45 jack. In addition, the transceiver preferably includes a plurality of electrically conductive pins connected to the circuit board and extending outwardly from the jack housing in an arrangement compatible with an RJ-45 jack. The pins may extend generally parallel to the circuit board.
In one embodiment, the signal connector means comprises a plurality of electrical contacts, and the at least one first circuit device comprises an active device, such as an integrated circuit. The IC may perform amplification, analog-to-digital and/or digital-to-analog conversion. The IC may accept a digital input signal and produce a digital output signal so that no analog signals are needed on the external mother board.
The at least one second circuit device preferably comprises at least one magnetic device. Accordingly, the EMI susceptible active IC is shielded from the relatively noisy magnetics.
According to another aspect of the invention, the communications transceiver may include at least one filter/termination device mounted on the circuit board adjacent the at least one active device. An electrically conductive member may be provided defining a second internal EMI shield between the at least one filter/termination device and the at least one active device.
In another embodiment of the invention, the signal communication is over a pair of optical fibers. In other words, in this embodiment, the signal path connector means comprises an optical detector for inbound optical signals, and an optical emitter for outbound optical signals. Thus, the at least one first circuit device preferably comprises a receiver circuit device, such as a receiver IC, connected to the optical detector. The receiver IC typically includes high gain amplification circuitry that is susceptible to EMI. The at least one second circuit device in this optical embodiment preferably comprises a transmitter circuit device connected to the optical emitter. The transmitter may also be in the form of an IC. The internal EMI shield carried by the circuit board protects the receiver from EMI generated by the transmitter.
A method aspect of the invention is for making a communications transceiver of a type comprising a jack housing including portions defining a recess for receiving a mating plug therein, signal connector means within the recess for establishing inbound and outbound signal paths with corresponding signal connector means of the mating plug, and a circuit board within the jack housing and connected to the connector means. The method preferably comprises the steps of: providing the circuit board with an electrically conductive layer defining a first internal electromagnetic interference (EMI) shield; positioning at least one first circuit device being susceptible to EMI on a first side of the circuit board; and positioning at least one second circuit device generating EMI on the circuit board on a second side thereof opposite the first side so that the first internal EMI shield extends between the at least one first circuit device and the at least one second circuit device.
The method may also include the step of providing an electrically conductive layer on outer surface portions of the jack housing defining an external EMI shield, and electrically connecting the first internal EMI shield to the external EMI shield. In one preferred embodiment, the jack housing and output pins are compatible with an RJ-45 jack.